Silver, which is commonly used in jewelry, is also known for its antimicrobial properties and has found widespread use in biological and medical applications. A large number of commercial medical products with antimicrobial silver are used in wound care and other medical applications. Silver has high electrical conductivity (63.01×106 S/m at 20° C.) and thermal conductivity (429 W/m·K) which has led to its application in electrical, electronics and thermal transfer fields. In addition, silver has very high reflectivity and low emissivity and has found uses in adaptive optics and in making items such as optical mirrors and reflectors.
Silver has been used to make conductive elastomers. Such elastomers may be found as sheets or gaskets and are filled with up to 60% of a fine powder silver and such constructs have high conductivities. These elastomers typically can maintain their conductivities even after being stretched by 300%. An example of use of such products is a sheet form of a silver powder-filled elastomer applied to the surface of a large object, such as an airplane. The silver powder-filled sheet absorbs radio frequencies thus making the surface invisible to radar. Such silver-powder elastomeric covered objects are potentially useful in military applications. Covering surfaces with these materials adds considerable weight to the object because sixty percent of the weight of the covering is silver or other conductive metal.
One approach to making lighter conductive elastomers is to apply a metallic layer only on the surface. The layer or coating is applied by traditional methods such as electro-less plating or vapor deposition. In general, coated fibers are not robust as the metal does not adhere well to the underlying elastomer substrate and often fail under even small strains. Coatings or layers of metals, such as silver, have been used on many types of fibers or other surfaces to render the surface antimicrobial or to resist growth of organisms, or to provide for a highly reflective surface. These coatings or layers often release metal, due to chemical or mechanical forces, and thus provide an unhealthy amount of metal to the environment or the surface fails to meet its intended use.
What is needed are methods and compositions for treating surfaces with metals, such as silver and others, so that the metal is retained on the surface and the surface is capable of meeting its intended usage for an extended time.